Who are Dzhokar and Tamerlan Tsarnaev?

WASHINGTON, D.C. (WUSA) -- The manhunt in the Boston Marathon bombings may be over, but the investigation is only the beginning. There are clues as to why they might have done what they're accused of doing, but no concrete motive. The brothers, who had come to the U.S. 11-years ago from the Russian region near Chechnya, could have had achieved the American Dream. Instead, they seemingly turned on the very country that granted them asylum.

When the FBI released the first picture of Dzhokar Tsarnaev on Thursday, a teacher at his old high school instantly thought he recognized him.

"People have said to me, 'Why didn't you call and say you could identify this person?' Because there is no way it could be this kid! There's nothing about him that would suggest anything like this - politics, religion, nothing," said Larry Aaronson, a teacher at Dzhokar's old high school.

The 19-year-old had been an all-star wrestler at Cambridge Rindge & Latin High School. A former teammate described him as cheerful and normal.

"He was a fun kid. He liked a lot of people. He had a lot of friends, diverse type of friends," said the former teammate.

Dzhokar was currently enrolled at UMass Dartmouth, which was on lockdown Friday. His friends said they saw him on campus Thursdayafternoon.

"It's crazy how you can know someone and never know what their planning," said a classmate.

But his older brother's alleged involvement may be less surprising. Tamerlan Tsarnaev had dropped out of a Community College in Boston where he'd been studying engineering. The 26-year-old was an accomplished boxer, but his teammate told CBS News that he noticed a change in Tamerlan about 18-months ago.

"The first time I met him, he had on leather pants and snakeskin boots. The second year I saw him he had on a t-shirt, hoodie, and jeans. The way he carried himself was much more humble. He only spoke about his faith. He was big into religion."

CBS News reports that Tamerlan hit the FBI's radar two-years-ago. He was even interviewed about possible ties to extremists, but the FBI says they failed to find a link. Last year, Tamerlan told a Boston University magazine "I don't have a single American friend. I don't understand them."

The brothers came to the U.S. 11-years ago from the Russian region near Chechnya. It's an area that's been plagued by an Islamic insurgency. Dzhokar listed "Islam" as his worldview on a Russian social media site. The brothers were both in the U.S. legally. Tamerlan had a greencard, and Dzhokar became a U.S. citizen on September 11, 2012.